FIGURE 1 .

(a) AFM single molecule experiments can pull pairs of atoms apart under a constant loading force F. By repeating the same experiment a number of times, one may determine the unfolding rate for a given residue pair and force. (b) A simple steric model of a pore. Assuming that the protein unravels as a consequence of being dragged through the pore, a special role will be played by the residues that contact the rim of the pore. Their identity depends not only on the site of the translocation initiation site but also on a possible partial unraveling of the protein in the region of the initiation site.